Note: Descriptions are shown in the official language in which they were submitted.
- 1 - 'I 119512-
Background of the Invention
As an alternative to chemical control of plant
pathogens such as bacteria and fungi, the use of natur-
ally occurring biological agents provide many advantages.
The use of biologicals should reduce the environmental
impact of chemicals as well as providing safety advan-
tages to non-target life forms.
The use of microbial antagonists for biological
control of plant pathogens can be considered as a specific
alternative to chemical control. The antagonist in the
natural state normally exists but at levels far too small
to produce a beneficial effect. However, it should be
possible to use an antagonist which normally is native in
such a way as to overcome the soil-borne pathogens by
either being present in such numbers as to destroy the
pathogen or inhibiting its growth by utilizing its normal
food supply. This invention describes the conditions
under which soil born pathogens can be controlled by a
microbial antagonist. With crops such as sugar beets,
soybeans, beans and the like, root rot, crown rot, damping
off, and other seedling diseases crease a serious econo-
mic problem. Seed treatment or soil amendment with a
chemical fungicide such as pentachloronitrobenzine (PCNR)
can be effective but the use of naturally occurring bio-
logical agents would be desirable.
Detailed Description of the Invention
Root rot, damping off and other seedling di-
seases are caused by soil borne pathogens such as of the
Rhizoctonia, PhYtophthora, PYthium, Fusarium, or Sclerotia
species. A fungus, Corticium sensu lato, antagonistic
to the noted soil born pathogens has been found to be
effective in the biological control of these pathogens.
The fungus can be utilized by coating seeds with it or
by using it as a soil amendment.
The antagonistic fungus, characterized by
mycelial clamp connections, was isolated from sugar beet
residue from western Nebraska. In culture and apparently
-2- 11~951Z
in soil, it produces reddish-brown sclerotia which may
help it survive for long periods. The fungus has been
identified as Corticium sensu lato, referred to here-
after as Corticium.
Example 1
Seed Treatrnent
In culture, Corticium parasitized various
Rhizoctonia solani isolates. Its potential as a bio-
logical control agent was tested by coating seeds with
Corticium and determining if these seeds were protected
against Rhizoctonia. Fungal material for coating seeds
was produced by growing Corticium on a liquid growth
medium for 14 days, collecting and air-drying the fungal
mat and grinding the material to a desired particle size.
Seeds were coated by dipping them into a methyl cellulose
solution and rolling them in ground Corticium of either
a coarse or fine particle size. Other seed treatments
included methyl cellulose and PCNB coated seeds, and un-
treated seed, PCNB being a fungicide active against the
_. solani pathogen. These seeds were planted either in
unamended greenhouse soils or in soils amended with R.
solani pathogenic to sugar beets. Plant stands recorded
after 2 weeks are summarized in Table I. In Rhizoctonia-
infested soil, seedling emergence from Corticium- and
PCNB-coated seeds was about the same and significantly
higher than seedling emergence from untreated and methyl
cellulose coated seeds. These results indicate that
Corticium and PCNB protected sugar beet seeds from damp-
ing-off caused by R. solani.
- 111951'~
T~BLE I
Comparison Between Corticium sensu lato and PCNB as
a Sugar Beet Seed Protectant Against ~hizoctonia
solani in Soil
_________________________________________________________
Seed Percent of Plants Emerged
Treatment w/o R. solaniw/R. solani
- Untreated 6~abl 5 f
Methyl cellulose 47 cd 2 f
Corticium coarse
mycelium 67a 55bc
Corticium fine
mycelium 62ab 24 e
PCNB (slurr ) 44 d 31 e
Y
lvalues followed by the same letter are not significantly
different at the 5% level.
Example 2
Corticium was also tested as a soil amendment to
control _. solani. Three different soils were amended
simultaneously with R. solani plus ground Corticium mycelium,
R. solani only, Corticium only, or left unamended. Untreated
seeds were planted in these soils immediately after amendments
were incorporated and percent seedling emergence was recorded
after 2 weeks. Soybean seed and . solanl pathogenic to
soybeans were used in sterilized sand and sterilized loam
while sugar beet seed and R. solani pathogenic to sugar
beets were used in field soil from Western Nebraska. The
average percent seedling emergence of 4 successive plantings
in these soils are shown in Table II. Higher seedling
emergence of soybean and sugar beets resulted from untreated
seeds of these 2 crops planted in soils amended with
Corticium and R. solani than in soils amended with R. solani
only. This indicated that Corticium added to soil protected
seeds and seedlings against damping-off caused by . solani.
mb/ - 3 -
~119SlZ
In control soils without R. solani, Corticium used either
as a seed coating (Table I) or added to the soil (Tablc II)
caused no reduction in seedling emergence and many times
increased it over controls. Survival of R. solani in soil
with Corticium significantly declined in 9 months in the
greenhouse when compared to soils with R. solani only.
Corticium survived much better than R. solani during this
period.
T~BLE II
.~
Performance of Corticium sensu lato Against Rhizoctonia
solani in Three Different Soil Types
Average Percent of Soybean or Sugar
Beet Plants Emerged in 4 Successive
Soil Amendmentl Plantings
Sovbean Sugar Beet
Sterilized Sterilized Field
Sand2 Loam Soil
- None 42a 57c 18e
Corticium mycelium 54a 66c 37 fg
R. solani 12 b 4 d 23ef
R. solani +
Corticium mycelium 58a 19 d 50 g
lall soil amendments were added simultaneously at the be-
ginning of the experiment.
2values followed by the same letter are not significantly
different at the 5% level.
Results from extensive greenhouse studies showed
that seed decay and seedling blight (damping-off) of sugar
beets caused by Rhizoctonia solani is reduced substantially
by coating the seed with Corticium. Similar results were
obtained when seeds were coated with the antagonistic fungus
and planted in a sugar beet field that had a very high
amount of _. solani. In greenhouse studies, higher seedling
emergence of sugar beets resulted from untreated seeds
of soybeans and sugar beets planted in soil simultanc-
ously amended with R. solani and the antagonistic
mb/ 4
~1195~2
func3u~s than in .soils amended ~litll R. _olani only. Sur-
vival of ~ solln in soil with the anta(3onistic fun(3us
signif icantly declined in ~ months in the greenhouse
when compared with soils with R. solani only. ~ihen
5 compared as seed treatments or soil amendMents, the
fungici(le PCNn and the antac3Oni,tic ruo(Jus y.lve nearly
e-lual protection a(3ainst seedling dampiny-of ~ caused
by R. solanl but the anta(3onist protection hac3 greater
longevi ty .
l~xample _
Greenhouse _rial__eed Treatments
The greenhouse studies evaluatinc~ ~seed treat-
ments involved the followinc3 treatments with f ield soil
from southeastern Nehraska:
15 Treatments:
1. Soil heavily infested with R. solani ancl planted
with untreated seed;
2. Same as treatment 1 except seed was coated with
Corticium, the antagonistic fungus;
20 3. Same a.s 1 except soil was not infeste(l with 1~. sl)lani;
4. Same as 2 except soil was not infested wi~ . s~ ni.
The yreenhouse trial comprised of 4 treatments
was repeated six times with essentially the same results.
Out of 32 seeds for each treatment, plantecl in 4 repli-
25 cated pots with 8 seeds/pot, the results sumarized inTable III were obtained. These results are representa-
tive of each of the six greenhouse trials.
11195~l2
lAUrr III
Iffcct o~ (`oating ';ugar neet Seed with C_r_ic_um
Sensu Lato to R. solani on incidencc of dampinc3-off _/
________________________________________________________
No. o Seedlings Seedling
Treatment _merc3ed out of_ _2 seec1s_ _emerc3erlce
Soil in~esteci~ith
R. solalli
1. Untreatecl seed 1 0.03
2. Seed coated with
Corticiurm fungus
antagonistic to
_. Solani 10 31-
Untreated soil (no r~. solani)
3. Untreated seed 12 37
4. Seed coated ~ith
Corticium antagonis-
tic fungus 14 40
a/ The suyar beet seed was of poor quality as only 60%
was viable.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ ~ _ _ _
~rom the results of these trials it is apparent that:
1. The fungus Corticium sensu _ato gave good
~rotection to suc3ar beet seeds and seecllings against
damping-off caused by R. solani. ~bout 31% of the
seedlings emerged from seeds treated with the antagonis-
tic fungus and plantecl in soil heavily infested with1~. solani (Table III). Only 0.03% of the seedlings
emerged from nontreated seeds plantecl ir- soil infested
~ith _. solani. Seedling emergence from untreated ancl
treated seec3 planted in soil free of R. solani was 37%
and 40%, respectively.
2. Seeds treated with Corticium sensu lato
and planted in soil free of R. solani consistently gave
higher stands tllall untreatec3 seed planted in the same
soil. This .suggests that the antagonistic fullyus pro-
tccts thc gcrminating ~sce(ls and sccdlill(~i from pathoc3ens
othc~r t~lan i~. solal-i.
~119SlZ
~xam~le 4
Greerlhouse Trials Soil ~mendlTlents
. ~
Tllree c3ifferent soils, two different Rhizoctonia
isolates, and seed of two diferent crop plants were used
in this study. Untreated soyhean seed and a soybean iso-
late of R. solarli were used in steril.ized sancl and steri-
_ _ . . _
lized loam. ~ntrc?ated suyar ~eet ce(l and a su(lar beet
isolate of R. solani were usecl in fielcl soil from we.stern
~ebraska. The soils were simultaneously amended with the
treatments inclicatecl and plante~ to 4 succes~sive crops of
untreated seed. The average percent seedlin~3 elnergence
a~ter 2 weeks i shown in Table IV.
Treatments (soil amendments)
1. I~]one
2. Corticium mycelium
3. R. solani
4. R. solani + Corticium mycelium
~ l` IV
Performance of C _t_ ium sensu lato ~gainst
~hi~octonla s_lani in Three Different Soil Types
_________________________________________________________
~verage ~ercent of soyhean or
.sugar beet ~lant.s emerged in 4
___successiv__~a_tln-~s __ __ _
1/ _ _____oybean _ _ __ ___ Su(3ar Beet
Soil amendment- Sterilized Sterilized
_ _____ __ ______ ___ Sanc3_ _____Loam __ Fi C? ld Soil
None?` 42a2/ 57 c 18 e
Corticium mycelium 54a 66 c 38 fq
R. solani 12 b 4 d 23 ef
R. solani ~ Corticium
myc;elium 58a 13 d 50 g
_ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ . _ _ _ . . _ _ _ _ . _ . ~
1/~11 soil am-ndlllents were aclded simultaneously at the ~e-
ginning of the experiment.
2/Vall]cs ~ollowccl hy thc same letter are not si~nificant-
ly llifr-~ lt~ t ~ c 5~ lc~v~l.
_________________________________________________________
111951Z
lli(3hcr seedling emer(3ellce o~ soy~ean ancl sugar
beets resulte(l 1rom untreated scec3s o~ these two erops
planted in soils amended with Cortieium and R. solani
than in soils amended with R. solani only. This indi-
eated that _orticium adde(~ to soil proteeted seecls andseec31inys against damping-ofE causec3 by 1~. sc)l<ln_.
Survival of I~. olani in soil with Co icium signifi-
eantly deelin~d in 9 morltlls in the greenilouse when eom-
. pared with soils with R. _olanl only. Cortieium sur-
vived mueh better than _. solani during this period.
Lxample 5
Field Trial
~ sugar beet field was used for this study.
This field had a high ineidenee of R. solani on sugar
beets (blaek rot) in 1976. In the trial, sugar beets
were planted on September 3 and eounts of seedlin~J
emergenee were made on September 13, 15, 18, and 20.
The sced used had a c3ermination rate of ~,0%. Thrce
seed treatments were used.
Treatments
___ _
1. Seed was not treated.
2. Seed was eoated with the fungus Cortieium,
antagonistie to R. solani.
3. Seed was treated with the antagonistie
fungus that hacl been ~illecl by steam heat
~ just before ~laeing it on the seed.
1,000 seeds were planted for eaell treatment.
See(31ing emergenee for the above three treat-
ments on September 15 was as follows:
Only 15~ of the untreated secds produeed seecl-
lings.
~bout 35% of the seeds treated with the antago-
nistie funyus ~rodueed seedlin~3s. This is more than
twiee the number produeecl by the untreatecl seeds.
The c3eaci anta(3onistic furl~3us (3ave no ~ otection
- a~3airls~ I~. _olani. C)rlly 1190 Or tile sccds coated with tl)e
dcad allta90rlistiC fU11~3US gave rise to seecllirl~3s.
" lil9512
Dam;)ing-off of suyar beet seeds and seecllings
was reduced greatly in a fielc3 with a hi~h amount of
R. solani by coatinc~ the seed with Cort _ium. The re-
sults from this field trial were comparable to those
obtainecl from cJreenhouse stuclies.
The oryanism Corticium sen.su lato appears to
be ubiyuitous in soil and has ~een isolated as a single
sclerotium. It has isolation inteyrity with respect
. to morphology and there has been no evidence toward
mutation. In a dry state, a mycelia-sclerotia mixture
has maintained viability for one year at 25 deyrees C.
It can be used for scccl coating or soil applications.
The organism is yrown via still culture with
yields averaging 12 grams per liter. It is yrown in a
potato-dextrose broth made by sliciny 300 grams of
potatoes to which is added 50n milliliters (ml.) of
distilled water. The potatoes are steamed until soft
and the broth is then strained. Distilled water is
adcled, if nccc~ssary, to yielcl a volume of 50n ml.
20 grams of dextrose is added to the potato broth
which is then sterilized by autoclaviny.
Various conventional techniques can be used
in culturing the organism and which can be summarized
as Lollows:
a. Flasks - 50 ml. media-still for 14 days;
aeration, 25 degrees C. 30 deyrees C.
or more results in sclerotia.
b. Plates - (100 ml. petri dishes) using
5 ml. depth - still - 3 days. Evaporate
to mycelial-sclerotia dry film.
shorter version of the techniquc has becn
to grow in flas};s for 2 clays and then pour
into plates as thin film and allow to pro--
ceed for 4 days more.
Beyinnin(3 at 5 days a dark wine-red cul-
turc filtrate is formcd. Thcrc is no
hioantayonistic activity in ~~ilt:ra~es.
~fter clryiny of the film, material can he
groun(l in a suitable mill.
", lll951Z
c. ~olid culture - rerlite used as the base
in 250 ml. flasks: 100 ml. ~erlite and
50 ml. of potato de~trose broth; 25 de-
grees C.
S Tl-is microbial antagonist to soil born patho-
may be utili~ed eEfectively in divcrsc formulations"
il~cluding the agronomically acceptahle aclj~lvants ancl
carriers normally employecd for facilitating the dis-
. ;~ersion of active ingredients for agricultural appli-
cations, recognizing a known fact that the dosage, formu-
lation, mode of application of a pest control a(3ent and
other variables may affect its activity in any given appli-
cation. Thus, the previously described antagonist may
be formulated as a suspension or dispersion, in aqueous
or nonaqueous media, as a dust, as a wettable powder,
as an emulsifiable concentrate, as a yranule, or as any
of several other known types of formulations, depencling
on the desired mode of application. These compositions
may bc applied as sprays, c]ust, or granules to the see(ls,
soil or plant situs against which activity is desired.
In order to provide compositions in the form
of dust, granules, water dispersible powders, aqueous
c~ispersions, or emulsions and dispersions in organic
liquids, the carrier or dilucnt acJcnt in ~such formula-
tions may be a finely divided solid, an organic liquid,
water, a wetting agent, a dispersing agent, or emulsify-
illCJ agent, or any suitable combination of these. General-
ly, when liquids and wettable powders are r)repared a con-
ditionirlg agent comprisinc3 one or more surface-active
agents or surfactants is present in amounts sufficient
to render a (~iven com~osition containing the active
material, the microorganism, dispersible in water or in
oil. The microorganism, the fungi Corticium _ensu lato,
is obtained by fermentation procedures. To convert it to
a form which will facilitate the preparation oE the fol-
lowing described compositions, a slurry is prcr)are(l which
i.s thell dLic?d onto a prim.lry, agronolnically ac(el~tc~l)le
carrier such as vermiculite, whereby the microorganism
-1 1- lll9S12
is adsorbecl onto the carrier. l`he micrOoryanism, ac]sorbed
OlltO the earricr, becomes the concclltrate for preparincl
the clesired composition. If desire(l, the slurry ean be
used as the concentrate for fungal antagonist compositions.
The surface active acJent used in the invention
can be a wettiny, dispersinc~ or emulsifyinc3 ayent which
will assist dispe~r~sion of the effeetivc comE)osition. The
surface-activ~ agent or surfactant can include SUCIl
. anionic, cationic anci nonionie agents as have heretofore
been generally employed in plant eontrol eompositions o
similar types. Suitable surfaee-aetive agents are set
forth, for example, in "~etergents ancl Emulsifiers" 1971
Annual by John W. I~leCuteheon, Ine.
In general, 1-10% by weight of the surface-
aetive agent will be used in eompositions of this inven-
tion and ordinarily the amount of surfaee-aetive agent
will range from 1-5% but may even be less than 1% by
weiyht.
~dditional surfaee-aetive agents ean be adcled
to formulations to inerease the ratio of surfaetants:
aetive incJreciients up to as high as 5:1 by weight. Sueh
eomE~ositions may have a yreater bioloyieal efectiveness
than can be exE,ectecl when the eomponents are usecl separ-
ately. When uscd at hic3her ratios, it it preferrecl that
the suraetant be present in the range of one-fifth to
five parts surfaetant for eaeh one part of aetive ayent.
~ The following are more detailed formulations
exemplifyiny the various eompositions.
~.xample 6
~ettable Powders
Wettable powders are water-dispersible eompo-
sitions eontaininy the aetive material, an inert solid
extender, ancl one or more surfaetants to provide rapi(]
wetting and to prevent heavy floceulations wherl sus-
pcnclccl in watcr.
` 1~1951Z
l'he inert extenders which are preferred for use in
the wettable powders of this invcntion containing the
active compounds are of mineral origin.
Extenders suitable for the wettable powder formu-
lations of this invention are the natural clays, diatomaceous
earth and synthetic mineral fillers derived from silica
and silicate. Most preferred fillers for this invention
are kaolinites, attapulgite clay, montmorillonite clays,
synthetic silicas, synthetic magnesium silicate and calcium
sulfate dihydrate.
Among the more preferred surfactants are the nonionic
and anionic types. They are most suitable for the preparation
of dry, wettable products of this invention and dispersants.
Occasionally a liquid, nonionic compound which is primarily
an emulsifier, may serve as both wetter and dispersant.
Most preferred wetting agents are alkylbenzene and
alkylnapthalene sulfonates, sulfated fatty alcohols, amines
or acid amides, long chain esters of sodium isethionate,
esters of sodium sulfosuccinate, sulfated or sulfonated
vegetable oils, and ditertiary acetylenic glycols. Preferred
dispersants are methyl cellulose, polyvinyl alcohol, lignin
sulfonates, polymeric alkylnapthalene sulfonates, sodium
napthalene sulfonates, polymethylene bisnap'nthalene sulfonate
and sodium-N-methyl-N-(long chain acid) taurates.
Wetting and dispersing agents in these preferred
wettable powder compositions of the invention are usually
present at concentrations of from about 0.5 weight percent
to 5 weight percent. The inert extender then completes the
formulation. Where needed, 0.1 weight percent of the
extendcr may be replaced by a corrosion inhibitor or an
antifoaming agent or both.
,, mb/ - 12 -
111951'~
Thus, wettable powder formulations of the
invention will contain from about 25 to 90 weight percent
active material, from 0.5 to 2.0 percent wetting agent,
from 0.25 to 5.0 weight percent dispersant, and from 9.25
to 74.25 weight percent inert extender, as these terms
are described above.
mb/ - 12a -
1~1951Z
-13-
~`~h('11 ~:h(` ~ et:tat)le p0W!ler C0ntCli11s a C(>rrOSiO!1
inhibit(>r or a1l a1ltifol1ninc3 IC3ent or botll, thi eorrosion
inhibi~or shoull not e-xeeed about l pcreellt of thc e~)n~
sition, and the a1ltitoamin~3 agc?nt shoulc3 not exeeecl a!~ut
0.5 1ereent t>y weic311t o~ tlle eomposition, botll rer)1a:in~3
e(~uivalellt amc)ullts of t,lle inert e~t.ellc3er.
rxam~>le 7
_ _ _ _ . _ _ _ _
~usts
_
Dusts are 3c?n.se powcler eompositionc, whieh are
intende~-] Lor ap~ eation in ciry form. nuSt~S are eharae-
terizec3 by their free-[lowinc3 and rapi`3 settling proper-
ties so that they are not readily winc1t)-)rll to areas
where their presenee is not desirecl. ~hey eontain pri-
marily an active inc3redient an~ a dense, ~ree-flo~7in~3,
solid exten(ler. Thcir performanee is sometimes aidecl
by the inelusio1l of a wettin3 a(3e1lt ancl eonvenienee in
manufaeture Lrequently demandci the ine1usion of an inc-rt
absorptive ~3rinc]in(3 aic].
The wettable powder as deseribecl above ean also
b~ u.e-1 in the preC)aration oL dust,. ~1hilc ,ueh wettahlc
powders ecln be used direetly in dust ~orm, it is rnore
advantac3c-ou.s to dilute them by blen-1inJ with the dense
3uit dilueilt. In this manner, (]is~er.iin1 a(JentC;l eorro-
sion inhieitors, anl alltifoarn ayents may also be used as
comporlel~ts o[ a c1ust.
I`huc, the duit eompciitio1ls oF thi-. invention
ean eomprise ~rom al)o1lt 0.5 to 20.0 wei~3ht peree1lt aetive
in3rcdiellt, 5 to 25 weigllt pcrecnt ~iller, () to 1.0 wei(~ht
prreerl~: wf?ttirlg a~3ent and ~rom about 30 to 90 weight per-
c(-nt den;e, fr(~e-~lowinc3 exten(3er, aci thcsc t--rms ar
u~ec31,(rein. ~ueh dust: I:ormulatiolls ean eortain, in
a,3ditic)ll, mi.nor amoullts o~ di.spersant~ci, corrosic>ll in-
hibitoLs, an(1 a1ltio;lm a(3ents 3erive(1 Lrom the wetta,le
~,;w<ler-; use(l t-~ make t11e dust.
111951Z
--I ,,--
F,xanl~le ~
~mulsif_able O_ls
Emulsifiable oils are usually solutions of sus-
pensions of active material in nonwater miscible solvents
together with a surfactant anc3/or emulsifier.
For compositions of thi~s invention, emulsi~iable
oil compositions can be made by mixing the active ingredi-
ent with an orc3anie solvent and surfactallt. Suitable
solvents for the compositions o~ this inventioll are
chlorinated solvents, water immiscible ethers, esters,
or ketones alone or in admixture with arolnatic hydrocar-
bons. Suitable surfactants are those ionic or nonionic
agents known to the art as emulsitying agents.
~mulsifying agents most suitable for the emul-
sifiable oil compositions of this invention are long chainalkyl or mercaptan polyethoxy alcohols, alkylaryl poly-
etiloxy alcohols, sorbitan fatty acid esters, polyoxy-
ethylene ethers with sorbitan fatty aci-3 esters, poly-
ethylene glycol esters with ~atty rosin acids, ~atty
alkylol amide condensates, calcium and amine salts of
fatty aleohol sul~ates, oil soluble petroleum sulfon(~tes,
or preferably mixtures of these emulsifying agents. Such
emulsifying agents shoulc3 comprise from about 1 to 10
weigllt percent of tlle total eomposition. ~s described
above, however, up to 5 parts of emulsifyinc~ agent for
eaeh part of active ingredient ean be used.
Thus, emulsifiable oil eompositions of the
present invention ean eonsist of from about 10 to 50
weight percent aetive ingredients, about ~0 to 32 perccnt
solvents, and about 1 to 10 weight percent emulsifier, as
these terms are defined and used above.
~_a~le_~
Granules
~,ranules are~ physically stable, particulate
c(~m~-O~.itions c~>llt:a;n;rlg Illycelium~ sclerotia ~"- spores
ol ~h;s inVelltiOn whicl~ adl~eL-( to or uL-c~(3i~ ril)u~e-1
Lhrough a basic matriY~ Or a coherellt, inert carrier with
lll~SiZ
microscopic dimensions. In ordcr to aid leaching of the
active ingredient from the granule, a surfactant can be
present.
The inert carrier is preferably of mineral origin,
and suitable carriers are natural clays, some pyrophyllites
and vermiculite. Suitable wetting agents can be anionic
or nonionic.
For the granule composition of this invention,
most suitable carriers are of two types. The first are
porous, absorptive pre-formed granules, such as preformed
and screened granular attapulgite or heat expanded, granular,
screened vermiculite. On either of these, a suspension of
the active agent can be sprayed and will be absorbed at
concentrations up to 25 weight percent of the total weight.
The second type are initially powdered ]caoline clays,
hydrated attapulgite or bentonite clays in the form of
sodium, calcium or magnesium bentonites. Water-soluble
salts such as sodium salts may also be present to aid in
the disintegration of the granules in the presence of
moisture. These ingredients are blended with the active
components to give mixtures that are granulated, followed
by drying to yield formulations with the active component
distributed uniformly throughout the mass. Such granules
can also be made with 25 to 30 weight percent active
component but more frequently a concentration of about 10
weight percent is desired for optimum distribution. The
granular compositions of this invention are believed to be
most useful in a size range of 15-30 mesh.
The most suitable wetting agents for the granular
compositions of this invention depend upon the type of
granule used. When pre-formed granules are sprayed with
active material in liquid form, the most suitable wetting
.,
~ mb/ - 15 -
~ll95~Z
agents are nonionic, liquid wetters miscible with the
solvent. These are more gencrally known in the art as
emulsifiers and comprise alkylaryl polyether alcohols,
alkyl polyether alcohols, polyoxyethylene sorbitan
mb/ - 15a -
~S~
11195:12
-16-
fatty acid esters, polyethylene glycol esters with fatty
or rosin acids, fatty alkylol amide concentrates, oil
soluble petroleum or vegetable oil sulfonates, or mix-
tures of these. Such agents will usually comprise up to
about 5 weight percent of the total composition.
When the active ingredient is first mixed with
a powdered carrier and subsequently granulated, liquid
nonionic wetters can still be used, but it is usually
preferable to incorporate at the mixing stage, one of
the solid, powdered anionic wetting agents such as
those previously listed for the wettable powders. Such
agents should comprise about O to 2 weight percent of
the total composition.
Thus, the preferred granular formulations of
this invention comprise about 5 to 30 weight percent
active material, about O to 5 weight percent wetting
agent, and about 65 to 95 percent inert mineral carrier,
as these terms are used herein.
